Peptide Nomenclature

Each of the twenty standard amino acids has a three-letter and a one-letter code — glycine is Gly or G, lysine is Lys or K. Sequences are written from the N-terminus (free amine end) to the C-terminus (carboxyl end), so Gly-His-Lys and GHK describe the same tripeptide.

Many peptides are best known by the code assigned during the research program that first characterized them — a manufacturer prefix plus a number. The same molecule may also carry a descriptive biochemical name and one or more informal names used in the literature. A reputable catalog listing resolves the ambiguity by stating the sequence or the exact compound identity alongside whatever name it sells under.

Synthetic peptides are isolated as salts — the peptide plus a counter-ion left over from purification. Acetate is the most common on research COAs; TFA salts occur when the purification acid is not exchanged. The salt form changes the gross weight of material in the vial (relevant to net peptide content) and can matter in sensitive assays, which is why the COA states it.

A complete label resolves to one molecule: name, modification state (e.g. amidated C-terminus), salt form, net content in mg, and lot number tying it to a COA. When two listings look like the same compound at different prices, compare those fields — differences in salt form, purity specification, or net content usually explain the difference.